http://pods.dasnr.okstate.edu/docush.../F-7663web.pdf
Here is the fungicide resistance group info and chart. Be careful you do not use the same fungicide repeatedly. Twice would probably be OK. And fungicides with similar chemistry count as the same fungicide. Resistance to one DMI fungicide is resistance to them all. Same for strobilurens.

Tall fescue is sensitive to brown patch in hot humid weather. Did your original seed mixture contain both tall fescue and perennial rye grass? A common situation...seed companies sometimes call this "Tall fescue mixture". Very misleading. And sometimes the perennial rye is lighter green than the tall fescue.
Brown patch info.http://www.turffiles.ncsu.edu/diseas...wn_Patch.aspx#

Bperl
I got off replying to the wrong person and thinking Duekster was the original poster, sorry.

I just took a second look at your photo's, when did this start? I take it was not 45 days ago and more recent?

I'm looking around the pic's at your's and neighboring yards and looks like it stops at the property line on each side of you and don't carry over into your neighbors yard? Diseased don't discriminate, much like a cancer it will spread unless your neighbors yard is treated with a preventative application.

I'm also seeing the second pic down on the left which looks like two green stripes and two yellow stripes all the way across the yard, did you spray anything or spread anything? The pic on the right of that looks like yellow grass and brown patch won't do that it will be green and only a circled area effected.

While I do not see a brown spot on the other side of the fence the turf looks mottled.

The grass seed that I've used was mainly 99% TTTF.
As mentioned before I did spray Weed B Gone Max with Crabgrass control (24D) around 45 days back. There was some discoloration in some parts of the lawn, but I thought it was normal for the grass to discolor a bit and then recover.

I guess the grass was weak and susceptible for disease invasion. Now that I think about it wasn't 45 days back that I've noticed this...but in the last 1 week or so..this has been spreading a lot. Today morning most of my lawn is looking brownish. Can't imagine how fast its changing. Luckily I don't see it spreading to my neighbor's lawn. Maybe because their lawns are more mature and disease resistant or maybe the seed I've used was not that resistant.

I read in couple of university websites that use of Organic fertilizers may(will) reduce the severity of the disease. I've bought Milogranite Organic fertilizer with Iron. Shall I go-ahead and spread it?

The grass seed that I've used was mainly 99% TTTF.
As mentioned before I did spray Weed B Gone Max with Crabgrass control (24D) around 45 days back. There was some discoloration in some parts of the lawn, but I thought it was normal for the grass to discolor a bit and then recover.

I guess the grass was weak and susceptible for disease invasion. Now that I think about it wasn't 45 days back that I've noticed this...but in the last 1 week or so..this has been spreading a lot. Today morning most of my lawn is looking brownish. Can't imagine how fast its changing. Luckily I don't see it spreading to my neighbor's lawn. Maybe because their lawns are more mature and disease resistant or maybe the seed I've used was not that resistant.

I read in couple of university websites that use of Organic fertilizers may(will) reduce the severity of the disease. I've bought Milogranite Organic fertilizer with Iron. Shall I go-ahead and spread it?

NO!!
Whatever you do don't spread that stuff it has nitrogen in it and will spread the fungus.

If its still spreading like you say and most of the lawn is brown we'll its sounding more like take all patch. I don't have much experience with take all but some of the other guys should chime in soon.

God created man, man plants grass, fertilized and watered the grass to watch it grow. Man cut grass and this confused God; in his infinite wisdom where did he go wrong? Why would man work, plant, water and once it grew cut it down just to see the process repeat.

Does Peat Moss help even the brown patch and/or Dollar spot ? I'm trying to see what if the lawn has more than one fungus. Wish I could narrow down to the root cause of the issue.

Don't know frankly.
There is little harm to adding this material as it wil build the soil too.
Yes, there is some expense which is why I suggested trying a bad spot and a moderate spot before treating the whole yard.

If you can get some under a magnifying glass or send off a sample to a pathology lab you could nail it down.

I can tell you peat works and works well for Take All and it is proven to work.